1. Field of the Invention
The present invention relates to water purification systems. More particularly, the present invention relates to a steam superheating device which vaporizes water into steam, then super heats the steam.
2. Description of the Prior Art
Many techniques have been employed for the treatment of impure water so as to provide a potable water supply. Generally the most widely employed techniques utilize distillation of one form or another, with wide variations in the source of heat energy being employed. Typically, heat energy is applied to the water by a first heating device which vaporizes the steam. In addition to vaporizing the water into steam, it has been known in the prior art to employ a second heating device to superheat the steam produced by the first heating device. An example of such a water purification apparatus is disclosed in U.S. Pat. No. 4,045,293 to Cooksley.
Cooksley discloses a water purification apparatus capable of treating water having impurities producing substantial foaming includes a boiler tank having a water inlet and a first heater for boiling the water within the water tank. A stack portion above the tank contains contact surfaces. A second heater is provided for heating the contact surfaces to a temperature above the vaporization temperature of water. In this manner water droplets which may be carried by the steam vapors from the boiler and/or foam will be immediately vaporized as it comes in contact with the contact surfaces. The steam vapors pass through a condenser assembly, and the condensate passes through a filter assembly before storage in a tank. The contact surfaces desirably comprises screen members providing a tortuous path and high heat conductivity. Baffle members may be interposed in the flow path for vapors from the boiler tank to the stack. Valves and a control circuit are desirably included to automatically control the volume of water in the boiler, to cut off water flow to components and to drain the assembly upon shutdown.
One of the major impediments to use of distillation involving rapid boiling of the water is the tendency for foaming to occur with certain types of contamination. This foaming often will require excessively large dimensions for the boiler or an intricate and elongated passage from the boiler to the condenser. Moreover, even with water feedstocks which do not evidence substantial foaming, rapid boiling will frequently produce a tendency for water droplets which are carded by the steam vapors into the condenser. As will be readily appreciated, foam droplets or such water droplets will exhibit the contamination of the feedstock and thereby contaminate the condensate which is produced.
In an attempt to eliminate the contamination posed by the feedstock, the prior an devices have employed a second superheating heater as described in Cooksley. However, one of the disadvantages in such a system as described above, is the requirement of two heating elements, one for boiling water to produce steam, and another for superheating the steam to vaporize the suspended water droplets in the steam. Dual heating elements accordingly require additional space, electrical connections, conduits, etc., adding to the complexity and cost of the water purification system.
Another problem which is frequently encountered in certain sections of the world involves the contamination of the water supply by organic compounds which vaporize along with the water in the boiler. Exemplary of such contaminants are carbon tetrachloride and chloroform which result from chlorination of water supplies containing dissolved methane and other hydrocarbons.
Various types of water purification devices have been suggested for providing potable water in the home, or on shipboard, or in other locations. Many of these devices require substantially continuous operation for efficiency, others require substantial investments, and still others require extensive maintenance from time to time.
It is an object of the present invention to provide a heating device for use in a water purification apparatus which can both boiler water to produce steam, and which can superheat the steam.
It is also an object to provide such a device which may be simply and ruggedly constructed to provide a durable and readily serviceable unit.
Another object is to provide such a device which is capable of substantially eliminating dissolved gaseous contaminants from water feedstock.
A further object is to provide a device whereby water feedstock containing impurities may be rapidly and efficiently vaporized without carry-over contamination in the vapor.
Numerous innovations for heating devices have been provided in the prior art that are adapted to be used. Even though these innovations may be suitable for the specific individual purposes to which they address, they would not be suitable for the purposes of the present invention as heretofore described.